1. Technical Field
The present invention relates to a head maintenance method that performs maintenance of a printing head having ink nozzles capable of ejecting an ink liquid by a cleaning operation, to a head maintenance device, and to a printer.
2. Related Art
As an apparatus including a printing head that has ink nozzles capable of ejecting an ink liquid, there is known an ink jet printer that performs desired printing onto a printing medium by causing the ink liquid to be ejected from the ink nozzles.
In such an ink jet printer, when a state where the ink liquid is not ejected from the ink nozzles, such as a standby state, continues for a predetermined time, water as a solvent of the ink liquid evaporates, viscosity of the ink liquid in the ink nozzles increases, and clogging occurs in the ink nozzles. As a consequence, the ink liquid may not be ejected, or even though the ink liquid is ejected, the ink liquid may not be ejected at an original size or speed, which causes defective printing (hereinafter, referred to as missing dot).
In addition, according to the use states of the printing head, for example, when the printing head repeatedly reciprocates, an ink meniscus in each ink nozzle is destroyed, which causes missing dot.
For this reason, in the ink jet printer, when the printing head is retracted at a standby position, the ink nozzles of the printing head are covered with a cap, such that an increase in viscosity of the ink liquid in the ink nozzles is prevented.
However, when a print processing is not performed for a long time, the increase in viscosity of the ink liquid in the ink nozzles may not be prevented by only covering the printing head with the cap at the time of standby. Further, when the print processing is continuously performed for a long time, the ink meniscus in each ink nozzle is destroyed during printing, which causes missing dot.
Accordingly, the ink jet printer has a cleaning mechanism that forcibly discharges the ink liquid having increased viscosity in the ink nozzles and recovers the ink meniscus.
A cleaning operation that is performed by such a cleaning mechanism includes a flashing operation, which causes the ink liquid to be ejected from the ink nozzles, and a suction and ejection operation where ink having increased viscosity or bubbles in the ink nozzles is discharged to the outside, and new ink liquid is supplied to each of the ink nozzles again by driving an ink suction pump connected to the cap and performing suction of the ink liquid remaining in the printing head for a predetermined time, and the like. In general, the suction and ejection operation requires more time compared with the flashing operation as a slight cleaning operation.
There is known an ink jet printer that, at a timing at which printing starts, that is, at a timing at which image data required for once scanning is stored in a printing buffer, selects a kind of cleaning operation according to the elapsed time from a last cleaning operation and performs cleaning of the printing head by the selected cleaning operation (for example, see JP-A-2003-103802).
However, in the known ink jet printer described in JP-A-2003-103802, the cleaning operation is performed immediately before printing starts, and thus a time at which printing actually starts is delayed by the time required for the cleaning operation. Accordingly, it takes additional time waiting for printing to end. In particular, when the cleaning operation by the suction and ejection operation is performed, it takes a considerably longer time waiting for printing to start.
For example, in a printer that prints a coupon to be issued to a customer at a checkout counter of a supermarket, when the cleaning operation by the suction and ejection operation is performed immediately before printing, it takes a longer time to deliver the coupon to the customer. Accordingly, the customer and waiting customers are kept waiting, and work efficiency at the checkout counter is degraded.